The present disclosure relates to an image forming apparatus, and in particular to a technique to save energy by lowering the temperature of a fixing unit.
Existing image forming apparatuses include a multifunction peripheral (MFP) having a plurality of functions such as copying, printing, and facsimile transmission. Such a type of image forming apparatus consumes large power and therefore, these days, reduction in power consumption is required, and energy saving standards are becoming more and more severe with time.
The power consumption by a fixing unit occupies a large portion of the power consumption of an MFP. For example, when a paper cassette is designed to accept 500 sheets of recording papers, the temperature of the fixing unit has to be set to a higher level, to prevent imperfect fixing even though 500 sheets are printed in one single printing job. While lowering the temperature of the fixing unit may lead to reduction in energy consumption, imperfect fixing may be incurred, when the temperature of the fixing unit is low.
To minimize the mentioned drawback, many of the existing image forming apparatuses are configured to perform the printing in an energy saving mode, in which the recording sheet is transported at a lower speed so that it takes a longer time for the recording sheet to pass the fixing unit, to thereby prevent imperfect fixing.
Here, when the recording sheet passes the fixing unit, the temperature of the fixing unit is removed by the recording sheet, and thus the temperature of the fixing unit is lowered. Accordingly, when a large number of sheets are printed in one single printing job, the temperature of the fixing unit is significantly lowered, and it becomes difficult to maintain the temperature of the fixing unit at a level required for the fixing. On the contrary, when only a small number of sheets are printed in one single printing job, the temperature required for the fixing can be maintained.
Accordingly, the mentioned image forming apparatus is configured to learn, in advance, the number of sheets printed in one single printing job, with respect to a section to which a user belongs, or to each of the users, and determine the setting for the energy saving printing, according to information of the number of sheets to be printed, acquired through the learning. For example, reducing the transport speed of the recording sheet by a smaller rate contributes to maintaining the productivity, which is desirable to the user. Therefore, the image forming apparatus only slightly reduces the transport speed of the recording sheet, when the number of sheets to be printed in one single printing job is small.